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Speaking of fire, a long time ago I read something from a switchgear manufacturers where you can install smoke detectors inside the switchgear. I guess the idea is that you could hook that into a SCADA system so that the workers can respond and gracefully bring down the system and find out what's going on. Not sure which vendor did that, or if all vendors offer that for low voltage gear.
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Jul 14, 2012 01:58
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Three-Phase posted:Speaking of fire, a long time ago I read something from a switchgear manufacturers where you can install smoke detectors inside the switchgear. I guess the idea is that you could hook that into a SCADA system so that the workers can respond and gracefully bring down the system and find out what's going on. Not sure which vendor did that, or if all vendors offer that for low voltage gear. On the project I'm working on right now, we have a fire suppression system (CO2 based, mobile equipment), that attaches to the control system. The PLC can trigger the CO2 dump, or can get notified when the fire system detects a fire and do things like trip the upstream MV breaker. I have seen switchgear with fire detection in it, but I'm not sure whether it was original or added later (but it was tied into the SCADA system, even showed on the HMI).
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Jul 14, 2012 05:58
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Here's my question - if you have equipment that's purpose is to protect equipment and the facility, should you have a different safety PLC or tie it into a fire protection system? If there's a fire at a facility, I can see where being able (or unable) to trip the MV upstream breaker would be a possible life safety issue for firefighters and personnel depending on the situation. Unless tripping the breaker might create more dangerous conditions like if you had ventilation blowers that would suddenly stop. Maybe if the CO2 system is really small or confined to a cabinet, it might not create a significant life safety risk?
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Jul 14, 2012 13:45
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Three-Phase posted:Here's my question - if you have equipment that's purpose is to protect equipment and the facility, should you have a different safety PLC or tie it into a fire protection system? If there's a fire at a facility, I can see where being able (or unable) to trip the MV upstream breaker would be a possible life safety issue for firefighters and personnel depending on the situation. Unless tripping the breaker might create more dangerous conditions like if you had ventilation blowers that would suddenly stop. The equipment room the CO2 protects is only ~8x14', and is normally unmanned during operation. Water would be impossible without mounting a tank, there's no permanent water lines to the cranes. The breaker is controlled by the control PLC, the safety PLC is not involved in the fire system operation (thankfully, else we'd have CO2 dumps every 5 minutes when it becomes unhappy). There can't be a general "facility fire" here; it's a container terminal where the entire yard is paved in stone and the e-rooms are on rail-mounted cranes (powered by a trailing cable that gets reeled in/out as they move down the track). If there is a fire, the firefighters will arrive after the CO2 dump (and thus MV breaker should be off). If the MV breaker somehow does not trip, there's a shutoff just upstream of it in the substation, ~300m away. As for the risk of the CO2 system, it has a 15sec holdoff, and there's a button to prevent CO2 release in the room it protects (but again, nobody should be in there during operation). For equipment needed to protect/evacuate teh facility, I'm not entirely sure on the protocol. I'll ask one of my friends in the mining division of our company what they do for mine hoists/blowers. Pretty sure all that stuff is switched off manually only though, no automated trip.
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Jul 14, 2012 14:49
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Fire suppression systems (sensors, alarms, fire pumps, etc.) in a building are generally powered from a dedicated breaker upstream of the main breaker, so that even when the main breaker is opened, there is still power to the fire suppression system. It gets a little more complicated when you add generators and UPS systems in, but there are pretty strict NEC requirements for what you can and can't put on a legally required emergency generator system. Sometimes, multiple generator systems are required so that one can be shut down while the emergency system stays up. It gets even more complicated when you have a "continuous industrial process" which is exempt from the shut-down requirements, but still requires protection if the fault/fire is somewhere within the continuous industrial process which can't safely be shut down. The interconnection between the fire suppression system and other safety systems like emergency power off buttons to provide an emergency shut-down signal is generally just a set of alarm contacts. The criteria for a shutdown is not necessarily when the alarms go off (fire alarm systems are notoriously whiney and always having nuisance alarms), but when something more fundamental occurs, like the flow sensor in a sprinkler pipe feeding a particular room sensing a discharge. grover fucked around with this message at 16:15 on Jul 14, 2012 |
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Jul 14, 2012 16:11
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This thread is great - I'm working at a utility this summer and as I'm reading through I realize how much I've learned outside of school in the past few weeks so far (I recognize the terminology and what some of the things do). So far I've really liked seeing a ~570MW powerplant, 500kV GIS substation and a brand new 500kV transmission line and sub that puts the 230kV underground. It is awesome seeing how huge some of the equipment is and learning about how it works. I also find it interesting how solar and wind present a lot of new challenges to the power grid and what is being done to try and adapt. Lt Moose fucked around with this message at 00:10 on Jul 15, 2012 |
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Jul 15, 2012 00:06
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Lt Moose posted:I also find it interesting how solar and wind present a lot of new challenges to the power grid and what is being done to try and adapt. I want a 1MV DC cross-continent tie from the west coast to the east coast, as well as a connection to Quebec hydro's grid.
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Jul 15, 2012 00:38
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Three-Phase posted:I want a 1MV DC cross-continent tie from the west coast to the east coast, as well as a connection to Quebec hydro's grid.   Probably gonna need some more dams...
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Jul 15, 2012 04:09
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The idea is you can link west coast, east coast, great planes (future windfarms?) and Quebec Hydro into one massive backbone. 2x2000kcmil (about 2400A in air, probably could be pushed higher than that for uninsulated line with some small amount of wind) at 1MVDC is only about 2.5GW.
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Jul 15, 2012 04:32
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Looks like MISO just put out a 'Max Generation Warning' for the Midwest. Hopefully we don't see rolling outages today.
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Jul 17, 2012 17:25
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Macintyre posted:Looks like MISO just put out a 'Max Generation Warning' for the Midwest. Hopefully we don't see rolling outages today. I've got my candles, matches, and some foodstuffs. How do you get these warnings? I'm assuming this stuff isn't for "public consumption" right?
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Jul 17, 2012 21:07
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When I get them its sent to a VP and filters its way down from there. Its pretty easy to tell when its going to happen though.
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Jul 17, 2012 21:23
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Three-Phase posted:I've got my candles, matches, and some foodstuffs. My boss is the manager of Electric T&D and he just forwards them onto us. Our company is just nearing peak generation as well; we started turning stuff off in our offices around noon (extra lights, non-essentials, etc). It's funny, 90 degrees is good for business. But 100+ degrees brings us to our knees.
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Jul 17, 2012 21:33
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It's 5:00 eastern, people are going to be going home and cranking up their AC's. This might get a little dicey.
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Jul 17, 2012 22:08
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My power was out from abuot 1:45-2:15 cst yesterday. First summer, non-storm-related outage in my neighborhood of more than a minute or two in the 9 years I've lived here. Not sure what the reason was.
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Jul 18, 2012 16:08
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ncumbered_by_idgits posted:My power was out from abuot 1:45-2:15 cst yesterday. The answer may lie in the last five posts in this very thread. Rolling blackouts.
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Jul 18, 2012 23:32
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I have two questions which I've been wondering about for some time (good thread btw): 1) How do they tension the cabling on power poles? It seems like there would be a ton of weight and force to bring them taunt. 2) I spent some time working in North Dakota after graduating from Uni and had a strange thought while driving for hours in the middle of nowhere: while it's well outside of the traditional goals of terrorism, namely fear, wouldn't an effective means of disrupting society be knocking out major electrical grid lines or stations in rural areas across the country? If you tipped over a couple towers in some farmers field simultaneously on major lines in the middle of nowhere, how much damage would it do and how long would it take to be repaired?
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Jul 22, 2012 21:22
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c0ldfuse posted:I have two questions which I've been wondering about for some time (good thread btw): I don't think you ever want them to be completely taut, although some may look that way. You need to allow for a small amount of sway as long as you don't let the phases get close enough to cause a problem. That also allows for heating/cooling and some leeway in case a power pole gets damaged. My guess is that the lines get bolted at each insulator, but they should be designed to have some sag and not be taut. quote:2) I spent some time working in North Dakota after graduating from Uni and had a strange thought while driving for hours in the middle of nowhere: while it's well outside of the traditional goals of terrorism, namely fear, wouldn't an effective means of disrupting society be knocking out major electrical grid lines or stations in rural areas across the country? If you tipped over a couple towers in some farmers field simultaneously on major lines in the middle of nowhere, how much damage would it do and how long would it take to be repaired? First - there have been incidents in the past where people damaged parts of the electrical grid on purpose - like shooting out insulators on power lines. I wouldn't rule out that a coordinated attack by knowledgeable individuals could cause a service disruption. However, they would need to have a good working knowledge of the power system. In many cases the power grid is more like a web. However there are some geographic locations that act as "power corridors" that could act as a weak spot. I was at a presentation where certain transmission lines were mentioned that were almost always running at full or overloaded capacity. There are places where an attack could cause a serious disruption. But physically damaging the large transmission line (>138kV) towers would take a lot of work versus someone trying to damage your bog-standard wooden 7200/13.8kV neighborhood distribution line. With that said, it's also important to not underestimate what the high-voltage linemen can do to repair damaged lines and systems. I've heard of instances where a storm comes through and these guys work their fingers to the bone to get people back online. Also, if a major part of the grid was damaged, there are often reciprocal agreements where if there's a bad disaster in area A, the linemen from areas B, C, and D converge to help out in A. One of my co-workers said awhile back when there were really bad storms, he saw a convoy of a dozen utility trucks heading down the highway to the affected areas. Also, one of the other concerns is substation security and the Aurora attack. Besides locks and remote monitoring, in a lot of substations the security is limited, and someone with either cyber or real-world access could potentially cause serious problems. Three-Phase fucked around with this message at 07:44 on Jul 27, 2012 |
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Jul 27, 2012 07:38
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Three-Phase posted:One of my co-workers said awhile back when there were really bad storms, he saw a convoy of a dozen utility trucks heading down the highway to the affected areas. That's nothing--I was in Carbondale, IL for this storm and they literally filled the dorms and the mall with linemen. There were 1,000 of them or something crazy like that, and they took a week to restore power. It was a sight to see, big parking lots full of the utility trucks--and orchard trucks that they used as utility trucks.
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Jul 27, 2012 13:10
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Who can spot the state which has had massive government subsidies for solar installations! http://www.pjm.com/about-pjm/renewable-dashboard/solar-power.aspx
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Jul 27, 2012 19:37
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c0ldfuse posted:
I work for a large utility contractor. We have a ton of guys that are generally able to leave their projects to go on "stormwork". These guys work 16 hours a day and can mobilize on a short notice. Utilities have something called "SCADA" which basically monitors electrical usage and they could figure out when power goes out pretty quick. Often times, buildings that it is vital to have power, they will have their own backup power. I would guess it would depend on the amount of damage they do. A crew can typically set anywhere from around 4-12 poles a day, depending on the soil, the crew, and pole size. If they knock over just a few poles, it wouldn't take long at all. I would say a large storm would have way more of an effect than terrorists knocking over poles. About a month ago, about 1.5M people were without power on the East Coast. Edit: However, if they took out the higher voltage transmission lines, like the 500 kv or 765 kv lines, that might take a bit longer The Sock fucked around with this message at 01:42 on Jul 28, 2012 |
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Jul 27, 2012 23:53
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So a neighborhood in the next city had a transformer fail. From the way the news is describing it, it sounds as if the transformer windings may have shorted.Local news posted:[Oncor] blamed the surge on hardware failure at a transformer. They believe dry soil at the base of the transformer may have contributed to the problem. This is one of the relevant articles. Thankfully it was limited to 6 houses, though there was 1 person injured from a light catching on fire. So how can dry soil cause a transformer to fail in such a spectacular fashion? And would a (good) surge protector have done any good in saving anything? And finally, assuming the houses saw 1kV or above, what else would be damaged? Breakers, wiring, etc? I'm assuming they saw at least 400-500 volts, since compressors got fried. The houses are new enough to have AFCI breakers, I would assume those got toasted along with GFCIs. edit: VVV looks like a good movie randomidiot fucked around with this message at 03:12 on Jul 28, 2012 |
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Jul 28, 2012 00:52
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some texas redneck posted:So a neighborhood in the next city had a transformer fail. From the way the news is describing it, it sounds as if the transformer windings may have shorted. Oh no. Oh no. It's happening... Three-Phase fucked around with this message at 02:09 on Jul 28, 2012 |
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Jul 28, 2012 02:05
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some texas redneck posted:So a neighborhood in the next city had a transformer fail. From the way the news is describing it, it sounds as if the transformer windings may have shorted. A high impedance ground could potentially have caused a lot of heat, but the symptoms would be dimming lights, not melting lights. I think this excuse is a cop-out. grover fucked around with this message at 16:35 on Jul 28, 2012 |
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Jul 28, 2012 16:23
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c0ldfuse posted:1) How do they tension the cabling on power poles? It seems like there would be a ton of weight and force to bring them taunt. Distribution-specific utility engineer chiming in here. Three-Phase is correct, we don't keep them taut, but depending on the installation, some lines may be tighter than others. An engineer in our Equipment and Standards group (where I work) prepares sag tables that show what sort of tension is suitable. It depends on all sorts of things like pole height, class (thickness), conductor size, load current, phase spacing, etc... That being said, I highly doubt any lineman actually builds to these standards. They more likely just tighten the lines to what looks right. We don't however bolt them on at each pole, most often the conductor is sitting on top of the insulator, and is held on with soft drawn aluminum ties twisted around them. Anyway, that's a long answer to a short question. If anyone has any questions from a utility perspective, ask away, I might be able to answer. This thread is a great read.
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Jul 28, 2012 18:24
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Theives have stolen all the ground wires on our utility poles, for a couple of blocks around. They cut them 1' and 6' above ground. What is the risk to my household electronics ( and mylife, I guess)?
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Jul 28, 2012 19:04
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some_admin posted:Theives have stolen all the ground wires on our utility poles, for a couple of blocks around. You may also want to avoid touching the grounds that haven't been stolen, as they're likely carrying a bit more current than usual and may be at a higher voltage above ground than normal. grover fucked around with this message at 19:17 on Jul 28, 2012 |
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Jul 28, 2012 19:13
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Killamajig posted:We don't however bolt them on at each pole, most often the conductor is sitting on top of the insulator, and is held on with soft drawn aluminum ties twisted around them. Ah, thanks for correcting me about them being bolted. About the report - remember that most likely neither the newscasters or the people involved (whose houses got messed up) are EEs, technicians, or electricians. I'm wondering if this whole thing might have been exaggerated. Three-Phase fucked around with this message at 02:31 on Jul 29, 2012 |
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Jul 29, 2012 02:23
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I work in an industrial setting. Our machinery is generally 3 phase 240 volt stuff. Motors, hydraulic pumps, nothing fancy. Most machines have 240 or 480 coming in and then somewhere along the line a transformer to 110 volts for the computer controller. My employer is steadfastly against protection against electrical surges. In the past 2 weeks we've lost one entire controller and the PSU on two other controllers. All were caused by lightning strikes or flickering power (it was storming). Is it a common practice to have zero protection? I realize it's a cost/benefit decision like anything else but we're really getting hosed over as parts are becoming increasingly hard to source as the machinery gets older. They don't even buy the standard $30 5 outlet surge protectors for their desktop computers or the server so I'm pretty sure they're insane. Common sense would tell you the benefit outweighs the cost when it comes to desktops and data storage. Now with industrial machinery, is protection for the entire shop an option? It would be 480 volt service. If we were to install surge protection at each machine, what is the likely cost realistically? Is it installed usually at the 240 end or after the transformer drops things down to 120? Is there any routine maintenance to perform on the surge protectors? How often are they typically replaced due to failure or as part of a replacement schedule? I want to make a proposal for them to start a plan for buying protection for at the very least machines with controllers that are custom built and impossible to replace. I once tried to convince the owners of using a capacitor bank either shopwide or per motor and even had an electrician price everything, and had worked out with the power company how much they'd potentially save per year. They were not interested. Hopefully I can do better with getting some surge protection.
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Jul 29, 2012 06:08
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I think you could install equipment at either the supply side (480V delta or wye) or at the pieces of equipment. It may be cheaper to add in equipment to protect the whole shop rather than to install at each piece of equipment. I like your plan to protect the most vital equipment, but the issue there is that you need to look really carefully at the system so you don't protect against situation A to end up getting screwed by situation B. You may also want to talk to them about upgrade plans or buying remaining stock of spares so you have at least one of each piece of super-critical equipment on hand. At least have some kind of "sealed attack plan" so you can respond in a timely fashion when your last piece of equipment fails - have a plan of how to replace it with something different. Also, are you 100% sure that all the damage is due to surges/lightning coming from the outside, and it's not possible that there are issues inside the building as well? Three-Phase fucked around with this message at 07:41 on Jul 29, 2012 |
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Jul 29, 2012 07:38
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There are issues with the building yes. One machine in particular had repeated failures of it's power supply and blown fuses on a near daily basis until some sort of conditioning and a UPS was installed. There are also stand alone mobile units that have problems only on some 240v outlets but fine in other areas of the shop. Having backups of some of the older systems would be prohibitively expensive, Some of the oldest equipment is from the late 70s but modified some time in the early 90s to take a digital controller. They cannot possibly be replaced, a modern controller would have to be installed. That's easy to do but time consuming. No single machine is more critical than any other. I guess what makes them 'critical' is that they're near impossible to repair. I think in general I know what I'd like to do, so I won't really bother you with any more questions about specifics. I just really wanted to get a feel for what the "best practice" or most common application is. Shop wide protection, per machine protection, per machine but only at critical locations, or no protection at all? If you roll into a factory and there's no protection, is that common or rare?
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Jul 29, 2012 08:16
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The only reason old facilities don't have it is because it wasn't invented yet when they were built; it's common to the point of ubiquity in newer facilities. MOVs are cheap, and there's no reason not to have one on every panel. Standard practice is to install one SPD at the main panel/service entry to protect from lightning strikes, and to install additional SPD at subpanels to protect against internal surges as well as provide additional protection against lightning strikes. Motors and switching transients are simply horrible for generating damaging transients in machine shops and other industrial buildings. The tools themselves can often take it, but the electronic controls can't. FYI, you can get a whole-house residential surge suppressor for about $20 for your own home, and probably should. grover fucked around with this message at 13:47 on Jul 29, 2012 |
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Jul 29, 2012 13:36
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I think that part of it depends on when and where the shop was built. Sometimes a plant in an industrial area might have a bad electrical neighbor. It's like where your apartment is. You may have a nice old lady next to you, or a punk rocker who answers to "Killer Dude". That and older equipment may have been more tolerant of PQ issues than new ones. Like Grover said, if it's a really old shop, I wouldn't be surprised at all if it was never built with much protection. One thing I'd suggest is hiring someone to do a power quality study in the building. Or you can lease a PQ device like a Dranetz and corresponding CTs for a year or so and do some studies yourself. You might be able to determine that one area or piece of equipment in the shop is giving the facility grief. With a PQ study, you can go from "some of our equipment crashes" to "typically at 7:45 AM, we have a severe transient that corresponds to equipment X starting up". I've troubleshot PQ issues in large facilities and solved some major power quality problems before, and it's amazing what a good device can capture. Be aware that these devices need some knowledge and skill to use. One of the coolest things I've done with Dranetz and Dran-View is to look at harmonic power plots. What's cool about that is you can get the direction that the harmonic power is flowing, positive or negative. So you may have a large VFD that's consuming power at 60hz, but is actually generating triplen harmonics that are going upstream into the power system. Here's what I'd look into: 1. Main panel suppressor 2. Isolation transformers for any large or noisy drives or similar devices like synchronous motor exciters 3. Separating power into a "clean" and "dirty" section. Maybe even a "very clean/UPS" section for very sensitive or mission-critical loads. If you want clean you'll want a double-conversion UPS, but those aren't cheap. You mentioned capacitors for power factor correction to save money with the power company - make sure you engineer any solution correctly. Switching in capacitors can cause nasty transients in the power system. Also, if you inadvertently run too far leading, like leaving the caps in all the time while turning the motors off, you can do weird stuff like having an overvoltage. Also, if you have a more complicated agreement to maintain power factor within a certain range (this is more for larger facilities, talking >10MW into the hundreds of megawatts) and you go outside that region for too long for whatever reason, you could get a nasty fine. Three-Phase fucked around with this message at 14:19 on Jul 29, 2012 |
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Jul 29, 2012 14:09
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Fantastic information, enough to keep me busy for quite a while, thanks! I do have a friend who works for the electric company as a service man for the past 25 years so I'll definitely be talking to him a lot. Thanks! 
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Jul 29, 2012 18:54
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One other comment on power quality studies: I've had some situations where customers ask "why don't we just use voltage instead of both voltage and current for our study/investigation?" You can hook up a PQ device with just voltage probes, and it will measure and report on voltage problems. However, when you have both voltage and current, you can do much more. For one thing, you can determine where a problem is occuring by looking at both the voltage and current. If my memory serves me correctly it works like this: Voltage up, current up: issue with the source (surge) Voltage down, current down: issue with the source (sag) Voltage up, current down: source stiffness issue at the source or issue with the load Voltage down, current up: issue with the load (overloading or motor starting) or source stiffness issue at the source I've seen those last two listed as being load-only problems. But I'm not sure I agree with that. (Grover - what is your take on my assessment here?) Not only that, but often the voltage and current waveforms will look very different, both offset because of power factor, as well as harmonics and nonlinear loads. One additional way you can sell this is to tell your boss that you can determine what stuff in the shop is costing them money for electricity. You can also determine if there's a potential problem with a piece of equipment. Say a 460V motor that has a nameplate of 10 FLA is actually pulling 11 or 12 amps and occasionally trips the motor overload.
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Jul 29, 2012 20:27
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Three-Phase posted:Voltage up, current up: issue with the source (surge) Unless it's something stupidly obvious, like the only large load in a small facility, tracing the specific source of a power quality issue can be very difficult. Especially intermittent ones.
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Jul 29, 2012 23:06
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The Sock posted:Three-Phase posted:And that make sense (IE quasi-internal knowledge of systems required to actually cause significant damage).
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Jul 30, 2012 01:09
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c0ldfuse posted:Thanks for the answers. They are putting in some new lines along a major freeway and I'm simultaneously impressed by the speed of some things and slowness of others. It depends on what they are doing, but as a rule of thumb they could usually put new wire in completely in 3 weeks/mile. Most of the work is done by contractors, and they usually get paid by performance. A lot of our power grid is pretty outdated. I was told the average age of it was about 40 years old.
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Jul 30, 2012 01:51
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grover posted:Unless it's something stupidly obvious, like the only large load in a small facility, tracing the specific source of a power quality issue can be very difficult. Especially intermittent ones. I've got to find the Dranetz book that quotes this stuff. Also, I'm assuming this is for stuff that's less than a few cycles.
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Jul 31, 2012 01:27
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Anyone heard about the power outages in India? Second time in 2 days their grid has almost completely collapsed. 600 million without power as of this morning.
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Jul 31, 2012 12:32
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